File represented by .ONE extension are created by Microsoft OneNote application. OneNote lets you gather information using the application as if you are using your draftpad for taking notes. OneNote files can contain different elements that can be placed at non-fixed locations on document pages. These elements may contain text, digitized handwriting, and objects copied from other applications including images, drawings and multimedia (audio/video) clips.
Files with PPTX extension are presentation files created with popular Microsoft PowerPoint application. Unlike the previous version of presentation file format PPT which was binary, the PPTX format is based on the Microsoft PowerPoint open XML presentation file format. A presentation file is a collection of slides where each slide can comprise of text, images, formatting, animations, and other media.
You can also convert ONE into many other file formats. Please see the complete list below.